1. Field of the Invention
The present invention relates to an antenna apparatus, and more particularly to an antenna apparatus which is used for receiving radio waves of a global positioning system (GPS), a satellite radio, and the like.
2. Description of the Related Art
Various antenna apparatuses have been developed as antenna apparatus which is used as, for example, an antenna apparatus of an in-car GPS system, which is wide-spread as a positioning system, an in-car antenna apparatus or an in-home fixed type antenna apparatus for a satellite radio, which has been put to practical use in the United States of America, and the like (see, for example, Japanese Patent Application Laid-Open Publication Nos. 2005-110007, 2004-72320, 2004-228357, and the like).
With respect to these antenna apparatuses, such as an antenna apparatus 100 illustrated in FIG. 6 for example, a circuit board 103 is attached on the back surface of an antenna element 102 including a patch type receiving surface 101 which receives radio waves. An amplifier circuit not shown, which amplifies a signal input from the antenna element 102, is formed on the surface of the circuit board 103 on the opposite side with respect to the antenna element 102 side, and the surface on which the amplifier circuit is formed is covered by a substantially box-like shield cover 104 which shields the amplifier circuit from external disturbing waves. Here, in FIG. 6, the receiving surface 101 is shown thicker than the actual thickness thereof.
An input pin 105 is provided to penetrate both the antenna element 102 and the circuit board 103 in a direction perpendicular to thereof, and one end side of the input pin 105 is electrically connected to the receiving surface 101 of the antenna element 102 by soldering. Moreover, the other end side of the input pin 105 is electrically connected to the amplifier circuit on the circuit board 103 by being soldered to the amplifier circuit, so that an input unit 103a is formed. The input pin 105 inputs a radio wave signal, which is received by the receiving surface 101 of the antenna element 102, to the amplifier circuit on the circuit board 103.
Moreover, a coaxial cable 106 is inserted into the inner side of the shield cover 104. A core wire 106a of the coaxial cable 106 is electrically connected to the amplifier circuit on the circuit board 103 by being soldered thereto, and the connecting portion constitutes an output unit 103b of the amplifier circuit. The coaxial cable 106 supplies driving power to the amplifier circuit through the core wire 106a, and outputs a signal that has been received by the antenna element 102 and has been amplified by the amplifier circuit.
Moreover, the shield cover 104 also serves as the ground (GND), where a tongue flap 104b, which is formed by being bent from the base surface 104a of the shield cover 104 to the side of the coaxial cable 106, is electrically connected to the outer conductor 106b of the coaxial cable 106 by being soldered thereto, thus allowing the shield cover 104 to be set to the GND potential through the tongue flap 104b. The amplifier circuit is grounded through the shield cover 104.
With respect to such antenna apparatus 100, as shown in FIG. 7 which shows the antenna apparatus 100 being turned upside down, in a case where the shield cover 104 is fixed in the state where the shield cover 104 covers the amplifier circuit, it becomes impossible to ascertain the existence and the quality of the soldering, the soldering using solder H and being soldered onto the amplifier circuit on the circuit board 103. This can be said especially for the soldering at a portion between the input pin 105 and the wiring of the circuit at the input unit 103a of the circuit as shown in FIG. 6.
However, in a case where the shield cover 104, which has been attached once, is removed in order to ascertain the soldering of the input pin 105, the operations of removing, ascertainment of the soldering, attachment and fixing of the shield cover 104, and the like, must be performed, and thus redundant processes increase in the manufacturing process of the antenna apparatus 100 and the operation becomes troublesome. Moreover, the repetition of the removal and the attachment lowers accuracy of the attachment of the shield cover 104 to the circuit board 103.
Moreover, even in a case where the soldering at the input unit 103a is not performed, signals are transmitted if the input pin 105 touches the wiring. In a case where the physical contact between the input pin 105 and the wiring is lost by changes within time, no signal is transmitted, and thus the antenna apparatus 100 no longer functions as the antenna. In a case where a user accordingly tries to ascertain the soldering of the input unit of the antenna that is out of order, the ascertainment cannot be performed unless the shield cover 104 is removed.